1. Technical Field
The present invention relates to a fixed or slide-type constant velocity universal joint used in a power transmission system in automobiles and various industrial machineries. The fixed-type or slide-type constant velocity universal joint is mounted on a drive shaft or a propeller shaft used in, for example, a front-engine, front-wheel drive (FF) vehicle, a four-wheel drive (4WD) vehicle, and a front-engine, rear-wheel drive (FR) vehicle. In particular, the present invention relates to a constant velocity universal joint including a recess-projection engagement configuration by which an inner joint component is connected to a shaft.
2. Description of the Related Art
For example, a drive shaft of an automobile has a configuration in which a slide-type constant velocity universal joint is mounted on one axial end of the shaft and a fixed constant velocity universal joint is mounted on another axial end.
In a tripod constant velocity universal joint (TJ) that is one slide-type constant velocity universal joint used as a connecting joint of the drive shaft, three track grooves are formed on an inner circumferential surface in an axial direction. The constant velocity universal joint includes an outer joint component (outer member) and an inner joint component (tripod component). The outer joint component has a roller guiding surface in the axial direction on both sides of each track groove. The inner joint component includes three leg shafts projecting in a radial direction. A rolling element (roller) is housed between the leg shafts of the inner joint component and the roller guiding surfaces of the outer joint component such as to rotate freely.
A Birfield constant velocity universal joint (BJ) mat is a fixed constant velocity universal joint includes an outer joint component (outer member) and an inner joint component (inner member). In the outer joint component, a plurality of track grooves are formed on an inner spherical surface along an axial direction, the track grooves being equal distances apart in a circumferential direction. In the inner joint component, a plurality of track grooves forming a pair with the track grooves on the outer joint component are formed on an outer spherical surface along the axial direction, the track grooves being equal distances apart in a circumferential direction. A plurality of balls that transmit torque are interposed between the track grooves on the outer joint component and the track grooves on the inner joint component. A cage that holds the balls is interposed between the inner spherical surface of the outer joint component and the outer spherical surface of the inner joint component.
A configuration in which the axial end of the shaft is pressed into an axis hole inner diameter of the inner joint component is used as a connection configuration between the slide-type constant velocity universal joint or the fixed constant velocity universal joint, and the shaft. A female spline is formed on the axial hole inner diameter of the inner joint component and a male spline is formed on an axial end outer diameter of the shaft as a recess portion and a projection portion running along the axial direction.
A hardening process by, for example, induction hardening or carburizing and quenching is performed on the axial hole inner diameter of the inner joint component on which the female spline is formed and on the axial end outer diameter of the shaft on which the male spline is formed, thereby forming hardened layers. Strength of the axial hole inner diameter of the inner joint component and the axial end outer diameter of the shaft is ensured by the hardened layers being formed.
The axial end outer diameter of the shaft is pressed into the axial hole inner diameter of the inner joint component, and the male spline and the female spline mesh. As a result, the shaft is fitted into the inner joint component. As a result of spline engagement between the shaft and the inner joint component, torque can be transmitted therebetween (refer to, for example, FIG. 2 in Patent Document 1: Japanese Patent Laid-Open Publication No. 2003-314580).
In a connection configuration between the inner joint component and the shaft such as this, there is that in which a stopper ring with a round cross-section attached to the axial end of the shaft comes into contact with a locking surface provided on the inner joint component, thereby serving as a dislocation stopper (refer to, for example, Patent Document 2: Japanese Patent Laid-Open Publication No. Heisei 8-68426).    Patent Document 1: Japanese Patent Laid-Open Publication No. 2003-314580    Patent Document 2: Japanese Patent Laid-Open Publication No. Heisei 8 (1996)-68426